Originally Published EMDM May/June 2009
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Ultrasonic System Safely Joins and Seals Fragile and Micron-Thin Medical Parts
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Soniqtwist technology from Switzerland-based Telsonic will not stretch membranes or produce perforations in materials being joined or sealed.
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Widely used in the plastics and automotive industries for joining, welding and sealing parts, ultrasonic technology has not achieved the same status in the med-tech sector. Because the technique can damage fragile parts and perforate thin-film membranes, its use in medical manufacturing has been limited. That is about to change, if Telsonic AG (Bronschhofen, Switzerland) has its way.
Conventional ultrasonic systems produce amplitude in the vertical plane to weld, join or seal parts. This can harm delicate electronic components and produce perforations in micron-thin seals and membranes. By contrast, Soniqtwist technology applies small circumferential amplitudes, allowing even fragile electronic components and membranes to be processed.
The converter in a Soniqtwist system is mounted tangentially to the booster axis instead of sitting on top of the booster to increase amplitude, as is customary in conventional ultrasonic systems. Reciprocal circumferential amplitude is applied to a specially designed sonotrode, or horn, which creates an ultrasonic friction weld of the upper contacted film, membrane or rigid component and the lower component. The vertical force from the electronic proportionally controlled pneumatic actuator collapses the molten joint and maintains a requisite amount of pressure until the weld joint has solidified.
Soniqtwist technology will not stretch the membrane nor will it produce what is called a “diaphragm effect,” which can lead to perforations of the membrane. Small amplitudes typically measuring 60 µm pp are applied in a circumferential manner along the perimeter of the seal. The torsional amplitude diminishes almost to zero at the centre of the membrane or film.
The unique characteristics of Soniqtwist also enable multiple membranes, in close proximity to one another, to be processed without causing any previously welded membrane to become dislodged or to lose its hermetic seal.
Suited for welding and forming thin-wall section components made from plastic, ceramic or aluminium materials, the process minimises particle production and size, thus supporting good automated manufacturing practices. The technique also can be applied to welding operations on housings that contain delicate electronic devices.
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